Electron tube for generating high frequency oscillations



Dec. 16, 1958 J. A. TOMNER ErAL 2,864,971

ELECTRON TUBE FOR GENERATING HIGH FREQUENCY OSCILLATIONS Filed July 2l, 1954 ,IPAB-I1. all; IIAVIIA zzo United States Patent O ELECTRON TUBE FR GENERATIN G HIGH FREQUENCY GSCHLLATIONS Sigvard 'Jean Agne Tomner, Hagersten, and Sven Gustaf Gustafsson, Solna, Sweden, assignors to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a corporation of Sweden y Application July 21, 1954, Serial No.'444,888

.Claims priority, application Sweden August 15, 1953 8 Claims. (Cl. S15-39.67)

This invention relates to an electron tube for generating high frequency oscillations, and specially a tube of this kind arranged for variabletuning, where the tuning and the coupling between the tube and the load may be varied withoutrmutual interaction.

The principle of the kind of electron tube, to which the invention relates, is described in the copending U. S. patent application Ser. No. 284,978, filed August 29, 1952, by H. O. G. Alfven and Dag Rommell, now abandoned in favor of continuation application Serial No. 646,169, led March 14, 1957. In the tube described, the electrons which are accelerated in an electrostatic field parallel to the magnetic field, exchange energy `with a high frequency electric field while oscillating to and fro. The tube comprises means to impart to the electrons a drift motion perpendicular to the electrostatic lield.

The invention especially relates to an improvement of the tube shown in Figs. 7a and 7b of the above U. S. patent application Ser. No. 284,978. This tube is an integrated part of a waveguide system, where a tubeshaped part of the waveguide acts as reector electrodes, while the anode is arranged centrally within said tubeshaped part of the waveguide.

It is known from the above U. S. patent application to connect a tuned circuit between the tube-shaped reflector electrode and the centrally arranged anode in order to get the high frequency electric field, which absorbs the oscillation energy of the electrons, oscillating between the reflector electrodes. It is also known to take out the generated high frequency energy from said tuned circuit. This arrangement, however, has the disadvantage that the coupling between the tube and the load, and thus the power available at the output, is influenced by the tuning of the high frequency circuit.

The purpose of the present invention is to make the coupling between the tube and the. load independent of the tuning, whereby a high output power is obtained throughout the whole tuning range and the nuence of the load on the tuning is reduced.

The above described electron tube, the discharge space of which is permeated by a magnetic eld, and in which electrons, which are accelerated in an electrostatic field parallel to the magnetic eld, exchange energy with a high frequency electric field while oscillating to and fro, comprisesV at least one cathode, one anode, one cylindrical rellector electrode and one collector arranged so that the anode is locatedcentrally in the discharge space limited by the reflector electrode, the collector electrode being located at one end of said discharge space and the cathode at the other end, the electric field formed between the reflector-electrode and the anode thus having a component directed perpendicularly to the magnetic iield, which component imparts a drift movement to the electrons perpendicular to said field and said component.

The electron tube according to the present invention is characterized by the high frequency power being taken out via the collector, while the tuning is performed by 2,864,971 Patented Dec. 16, 1958 2 means of a tuning arrangement separated from the power output. The power output is arranged between the collector, which is provided with a central hole, and an inner conductor coaxially mounted in said hole.

The invention will be more closely described with reference to the accompanying drawing, of which Fi'g. 1 shows one embodiment of a tube according to the invention, Y

Fig. 2 shows a section along the line 2-2 of the tube shown in Fig. 1,

Fig. 3 shows another embodiment according to the invention.

An "embodiment of the electron tube according to the invention is shown in Fig. 1. The tube shown in Figs. 1 and 2 comprises within an envelope 40 a cathode 1, locatedin an aperture in a tube-shaped reflector 'electrode 4, land a cylindrical anode 2. The inner surface of the reflector electrode 4 and the outer surface of anode 2 dene an elongated annular discharge space. At the upper end. of this discharge space as shown in Fig. l a tubular collector electrode 7 is arranged, while cathode 1 is located near the opposite end of the discharge space. The cathode 1 isso arranged, that a diameter through the cathode forms an angle a. with a diameter perpendicular to the magnetic iield B, as s shown in Fig. 2. The cathode Y1, which is supported by the cathode leads 45, is vmanufactured of tantalum, tungsten or thoriated tungsten, and 'it is spiralized in the usual manner to increase the emitting surface without increasing the heater current required. The anode 2 is preferably manufactured of tantalurn, whereby a gas absorbing getter action is obtained, and a special gettermay be avoided. The anode is cylindrical, as a round anode gives an almost parabolic voltage distribution if the rest of the electrode system is suitably shaped, as is seen from Fig. 4 of the above mentioned U.V S. patent application Ser. No. 284,978. In the tube according to Fig. 1, the high frequency oscillations arertaken out from the collector 7, which to this end is provided with an inner conductor 104, for example of Kovar, to facilitate the glass sealing at 123, andwith an outer conductor of copper constituting a coaxial line. A sleeve 41 of Kovar surrounds Vthe collector and thus also the outer conductor 105. Said sleeve is sealed to theV glass seal 123 and the envelope 40. The reliector 4 is shaped as a sleeve and is prolonged upwards in the tube with a portion 124, so as to surround the collector. A ceramic supporting ring 121 separates the sleeve 41 and said portion 124 from each other and another supporting ring 122 keeps the inner conductor 104 in position withinv the electrode system. A tuning means is fastened to the lower part of the tube and is constructed to be the equivalent of that shown and described in connection with Fig. 3. The mutual'position of the anode 2, the reflector 4 and the cathode, 1 is made evident in Fig. 2, in which B indicates the Yexternally generated magnetic field.

wirhthe embodiment Shown in, Figs. 1 and@` it isi possible to adjust the coupling factor between the load andthe tube by setting the space or gap between the.

central Vconductor 104 and the anode 2.

`By means of providing the reflectorelectrode 4 withv a sleeve 124 enclosngthecollector'electrode 7 and having a length of'one-quarter wave length, as, is shownv` other figures. 128 is a tapping terminal for a coaxial line for taking out the high frequency effect between the sleeve 41 pertaining to the collector and the central conductor 104. The collector electrode 7 is coupled to' the reflector by the enlarged collar at the lower end`of the collector, which also encloses the latter to prevent the escape of stray electrons from the discharge space.

As is shown in Fig. 3 the electrode system is mainly composed of the cathode 1, the cylindrical anode 2, and the hollow, cylindrical reflector electrode 4. The electrons emitted from the cathode 1 are by means of the electrostatic field set up between the anode 2 and the reflector electrode 4 and the magnetic field beta (Fig. 2) caused to oscillate substantially in a plane', the projection of which in Fig. 2 is a line parallel withth'e magnetic field and intersecting the cathode. Owing to electrostatic field components perpendicular to the magnetic field and said last mentioned field the electrons are forced to move along the discharge space between the anode and the reflector electrode against the collector electrode 7. The reflector electrode 4 is extended out of the envelope by means of a metallic sleeve 101, made for instance of Kovar, vacuum sealed to the glass bulb 40 of the tube. The anode 2 of the tube is also extended out of the envelope and the vacuum seal is made against the Kovar pin 100, which forms a connection between the inner anode 2 and the inner conductor 134 of the coaxial resonator. In order to insulate the outer conductor 135 of the coaxial resonator from the reflector electrode 4 for direct currents, but to allow the passage of high frequency current, the outer conductor 135 of 'the coaxial resonator projects into the sleeve 101 a distance equal to a quarter of a wave length. Between the sleeve 101 and the outer conductor 135 is located a tube of insulating material, for example, Teflon. The outer conductor 135 is vacuum sealed on the one hand to the sleeve 101 and on the other to the inner conductor pin 100. The sleeve 101 and the part of the `outer conductor 135 of the coaxial line projecting into the sleeve form a quarter wave transformer coupling the electrode system of the tube with the coaxial resonator formed by the outer conductor 135 and the inner conductor 134. The coaxial resonator is tuned by means of the adjustable metallic plunger or slider 102, which short-circuits the coaxial line, whereby the effective length of the coaxial resonator and thus the resonant frequency of said resonator, which constitutes the tuned circuit of the tube is changed. The means for adjusting the tuning of the coaxial resonator, i. e., the position of the plunger 102, is the handle 108. The tuned circuit of the tube 120 according to Fig. 1 is constructed in almost the same way as in the tube according to Fig. 3, except the plunger 102 is operated by means of the knob projecting through the slit made in the outer conductor 135. In both of these constructions the tuned circuit is not directly connected to any load and no energy is thus taken out from the tuned circuit.

The output is taken from the electrode system 1, 2, 4 by means of the coaxial line 7, 104, the outer conductor of which also serves as collector of the tube. The coupling between the tube and the load, which is connected to the coaxial line 7, 104, is determined by the capacitative coupling between the anode 2 and the center conductor 104 of the coaxial line, i. e., the gap between them. With this arrangement the tuning is almost independent of the load.

We claim:

1. In an electron tube, in combination, an anode; a cylindrical reflector electrode spaced from and surrounding said anode and providing a discharge space; a collector electrode positioned at one end of said space; a cathode near the other end of said space; means providing a magnetic field permeating said space normal to the axis of said reflector electrode; an electrostatic field formed parallel to the magnetic field by anode-cathode potential having a component directed perpendicular to the magnetic field to impart a drift toward said collector electrode to electrons accelerated by the electrostatic field and oscillating therein; means indirectly coupled to two of said electrodes for taking out the high frequency energy from the collector electrode; a tuned circuit comprising a coaxial resonator separated from the said energy output; and means coupling the electrode system of the tube with the said coaxial resonator.

2. An electron tube as claimed inclaim 1, characterized by the tuning circuit comprising a coaxial line, the inner conductor of which is connected to the anode and the outer conductor of which is capacitively connected to the reflector electrode, said coaxial line being provided with an adjustable short-circuiting plunger.

` 3. An electron tube, the discharge space of which is permeated by a magnetic field, and in which electrons accelerated in an electrostatic field parallel to the magnetic field exchange energy with a high frequency electric field while oscillating to and fro, said tube comprising an envelope enclosing; an elongated anode, a cylindrical reflector electrode surrounding said anode and providing between them the discharge space, a collector electrode near one end of said reflector out of contact therewith and substantially closing the space against electron escape, and a cathode near the other end of said reflector positioned to effect an electric field between the reflector and anode having a com-ponent perpendicular to the magnetic field for imparting a drift to electrons from the cathode perpendicular to said magnetic field and to said component; a tuned circuit including an extension of said anode, a sleeve coaxial to said extension and having a high frequency coupling to said reflector, and an adjustable, short-circuiting plunger acting between said extension and sleeve; and a coaxial output circuit coupled to the anode-collector circuit.

4. The electron tube of claim 3 in which said coaxial output circuit includes said collector and a central rod capacitatively coupled to said anode.

5. The electron tube of claim 3 in which said coupling of the tuned circuit to said reflector comprises a quarter wave length insulated telescoping of the coaxial sleeve and a tubular extension of the reflector electrode.

6. The electron tube of claim 5 in which said extension is sealed into the envelope and to said coaxial sleeve which is sealed to said anode.

7. The electron tube of claim 6 in which the short circuiting plunger is an annulus outside the envelope movable between the anode extension and said coaxial sleeve.

8. The electron tube of claim 4 in which said coaxial output Acircuit includes a quarter wave coupling between the reflector and collector electrodes achieved by noncontacting partial telescoping of these electrodes.

References Cited in the file of this' patent UNITED STATES PATENTS 2,406,370 Hansen et al Aug. 27, 1946 

